# Development of a Liquid Microbial Enzyme Synergistic Fermentation Process for Strong-Aroma and Soy-Sauce-Aroma Fresh Distiller’s Grains and the Evaluation of Their Nutritional Value in Pigs

## TL;DR

A new fermentation process improves the nutritional quality of distiller’s grains for use in pig feed.

## Contribution

A microbial–enzyme synergistic liquid fermentation process was developed and optimized for two types of distiller’s grains.

## Key findings

- Crude protein increased while crude fiber decreased significantly after fermentation in both grain types.
- Fermentation improved amino acid digestibility and altered the microstructure of the grains.
- Optimal fermentation conditions were identified for strong-aroma and soy-sauce-aroma grains.

## Abstract

This study applied a composite microbial–enzymatic synergistic liquid fermentation process to strong-aroma and soy-sauce-aroma distiller’s grains. After fermentation, the crude protein content of both types increased significantly, while the crude fiber content decreased. Microstructural analysis showed improved structural characteristics. Fermentation also significantly enhanced the standardized ileal digestibility of most amino acids. The findings confirm that this process effectively improves the nutritional quality of distiller’s grains, supporting their utilization in pig feed.

China annually produces around 20 million tons of distiller’s grains, whose utilization is important for resource efficiency. These grains are rich in crude protein (CP), crude fiber (CF), and other nutrients, though their composition varies by grain type. This study applied a microbial–enzyme synergistic liquid fermentation process to two types—strong-aroma and soy-sauce-aroma grains—using a composite inoculant (Lactobacillus, Saccharomyces cerevisiae, Bacillus, each >1 × 109 CFU/g) along with xylanase, cellulase, and protease. Optimal fermentation conditions were identified: for strong-aroma grains—water-to-grain material ratio 1.8, inoculum 0.25%, 25 °C, 16 h; for soy-sauce-aroma grains—ratio 1.8, inoculum 0.3%, 25.5 °C, 13 h. After fermentation, CP increased by 13.62% and CF decreased by 30.37% in strong-aroma grains, while in soy-sauce-aroma grains an 8.83% CP increase and 31.31% CF reduction were observed. Structural analysis of both grains showed looser fibrous formations and changes in protein secondary structure.